Vandiver, J.K., Marcollo, H., Swithenbank, S., and Jhingran, V., Paper number OTC-17383, Proceedings of Offshore Technology Conference (OTC), 2-5 May, Houtson, Texas, USA, 2005.


This paper presents the initial results from VIV (Vortex-Induced Vibration) field testing of a long, flexible, model riser at high mode number. The experiments were designed to better understand the dynamic behavior of a long riser in uniform flow responding at mode numbers from 10 to 25 in cross-flow vibration. The 1.31 inch, (0.0333 m), diameter riser model was made from fiberglass line pipe, manufactured by Fiberspar Corp. Two model configurations with length of 201 feet (61.26m) and 401 feet (122.23m) were towed behind a vessel in a deep lake in upstate New York. Motion was recorded with twenty four evenly spaced internal tri-axial accelerometers. Observed reduced velocity and RMS displacement response levels are reported. Mean drag coefficients and hydrodynamic damping derived from measured data are compared to calculated values from formulas commonly used in engineering design of offshore systems.


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